201 research outputs found
Seismic retrofitting of an existing Chinese building with passive energy dissipation devices according to the design procedures proposed by Bergami et al. and Zhou et al.
No full textAfter recent strong earthquakes in China, the new Chinese seismic code was issued in 2011 in order to update protection categories for the school buildings and seismic intensities of some cities. As a result, a lot of school buildings need to be retrofitted to satisfy the new seismic code requirements. Therefore the use of Passive Energy Dissipation Devices (PEDDs), such as the Viscous Damper (VD), Metallic Damper (MD) and Viscoelastic Damper (VED), that are popular strategies for seismic retrofitting, are frequently selected by designers. This paper aims to evaluate the effectiveness of using PEDDs as retrofitting technology to upgrade an existing school building with devices designed through direct displacement based [1] or force based design procedure [2]. For that purpose, a real school building located in Shanghai has been retrofitted with Buckling Restrained Braces (BRBs) designed according to the two approaches, and then the structural performance of the different versions of the buildings was evaluated by subjecting each one to a set of seven ground motions recommended by the code. Finally, the seismic effects of different strategies (VD, MD and VED) following the force based approach are discussed in detail
Design of Additional Dissipative Structures for Seismic Retro-fitting of Existing Buildings
No full textAbstract: This paper presents an innovative approach for improving the seismic protection of existing
structures by introducing an additional dissipative structure (ADS). The seismic energy impacting the building
can be dissipated through the contribution provided by the ADS, thereby reducing the need for the existing
building to ensure its own seismic capacity. This retrofitting technique is well-suited for structures facing
architectural restrictions or challenging-to-update elements. It can help address foundation issues by applying
loads to new external components. This paper describes the design of the ADS and proposes a displacementbased
design procedure. The design process involves a non-linear static analysis and a simple procedure that
must be iteratively repeated until the retrofitting target is achieved. This approach is simple and
computationally efficient and can also be used for complex and irregular structures. Such structures are
frequently encountered, and existing structures often exhibit unusual geometries and materials requiring
extensive numerical modeling. The efficacy of the technique was evaluated using two case studies involving a
school building and a hospital located in central Italy. The results of numerical analyses indicated that owing
to the ADS’s contribution, the seismic capacity of both the buildings was enhanced, addressing the challenges
associated with complex foundation interventions
Masonry infilled r.c. frames Implementation and experimental verification of models for nonlinear analysis
No full textA design procedure for the seismic protection of infilled frames by dissipative braces. In: Proceedings of
No full text<p>Existing reinforced concrete frame buildings with non-ductile detailing suffered severe damage and caused loss of life during earthquakes. Different rehabilitation systems have been developed to upgrade the seismic performance of this kind of structures. The research discussed in this paper, carried out under the partial financial support of “convenzione Dipartimento di Protezione Civile- Consorzio RELUIS, signed 11/07/2005 (repertorio n. 540), research line 2, deals with the seismic protection of frame structures, in particular for the application presented buckling restrained steel braces (BRB) have been selected. A displacement-based procedure to design dissipative bracing for the seismic protection of frame structures is proposed and some applications are discussed. A two- fold performance objective is considered to protect the structure against the collapse and the non- structural damage by limiting global displacements and interstorey drifts. As an example, some r.c. frame buildings, designed according to the non-seismic Italian Code, have been analyzed also considering the infills and retrofitted with BRB via the proposed procedure. In order to assess the effectiveness of the proposed rehabilitation design procedure non linear static and dynamic time- history analyses have been performed. Concluding the necessity of performing dynamic analysis, instead of non linear static analysis, on structures with dissipative bracing systems has been discussed.</p></jats:p
Seismic upgrading of r.c. frame structures using a displacement based design procedure performed with OpenSees
No full textA displacement-based procedure [1] to design dissipative bracing for the seismic protection of frame structures has been developed and some application developed with OpenSees are discussed. The procedure does not require sophisticated dynamic nonlinear analyses but only common non linear static analyses and is based on the displacement based design. Two performance objective have been considered developing the procedure: protect the structure against structural damage or collapse and avoid non-structural damage limiting global displacements and interstorey drifts. The procedure has been tested on case studies of r.c. frame building, considered both bare and infilled, modelled with OpenSees [2]. Infills have been represented by means of single strut elements with a constitutive model calibrated on experimental base [3]: experimental tests have been performed on r.c. portal samples, bare and infilled. The tests have been prepared using OpenSees numerical simulations and, finally, those models have been calibrated in order to obtain reliable numerical models
Indagine sperimentale e numerica sul comportamento ciclico di telai in c.a. tamponati
No full textUnder seismic loads the interaction between masonry panels and the concrete structure of infilled frames (a very diffuse structural type in Italy) may generate stress and strain concentrations in r.c. elements (particularly in columns) and brittle failure behaviour can be detected due to these mechanisms.
The non-linear constitutive models for masonry, currently available, are calibrated to predict accurately the global response in terms of forces in masonry panels, and not to analyze local and global failure interaction mechanisms of panels and r.c. frames.
Through an experimental investigation information about the real behaviour of masonry infilled frames under seismic action have been gathered; with special attention on stresses and forces, but also on global and local failure mechanisms. Experimental tests performed at the Laboratory of experiments on materials and structures of the University Roma Tre, on bricks, mortar, single and double infill walls and finally on bare and infilled r.c. portals, are described and discussed.
In parallel with the experimental activity non linear fiber structural models representative of the considered structures by means of triple strut nonlinear cyclic models for masonry panels have been set up.
The accuracy of the models has been assessed through comparison with experimental results obtained form cyclic tests of frames
A design procedure for seismic retrofitting of reinforced concrete frame and concentric braced steel buildings with dissipative bracings
No full textThe research presented in this paper deals with the seismic retrofitting of existing frame structures by means of passive energy dissipation. An iterative displacement based pro cedure, based on capacity spectrum is described and some applications are discussed. The general procedure has also been discussed referring to the case of existing steel concentric braced frame structures (CBF). The procedure can be used with any typology of dissipative device and for different performance targets. In this work the procedure has been applied, with both traditional pushover (load profile proportional to first mode) and multimodal pushover, to an existing r.c. frame building. In the application presented the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The use of multimodal pushover proves to be more effective than pushover based on single mode in case of medium rise r.c. frame building (higher than 30 metres) but, once this building is retrofitted, and therefore regularized, with a bracing system, the difference between using monomodal or multimodal pushover becomes not significant
Proposal and application of the Incremental Modal Pushover Analysis (IMPA)
No full textIn recent years, many research activities were undertaken to develop a reliable and practical analysis procedure to identify the safety level of existing structures: Incremental Dynamic Analysis (IDA) is considered to be one of the most accurate methods to estimate the seismic demand and capacity of structures. However, the executions of many complex and computationally heavy nonlinear response history analyses (NL-RHA) are required. This paper deals with the proposal of an efficient Incremental Modal Pushover Analysis (IMPA) to obtain capacity curves by replacing the nonlinear response history analysis of the IDA procedure with Modal Pushover Analysis (MPA). In this work, the MPA is extended and applied to three-dimensional asymmetric structures and finally it is used in order to obtain a "multimodal" capacity curve: therefore MPA method is used to evaluate both displacements, as in the standard method, and base shear (this is a novelty). According to this approach the proposed procedure (IMPA) is defined and applied to estimate the structure's seismic response and capacity for given seismic actions. This new procedure is finalized to obtain a capacity curve, as commonly done performing pushover, but it accounts also higher modes effects. Finally IMPA is applied to an existing irregular framed building and compared with NL-RHA
A design procedure of dissipative braces for seismic upgrading structures. 2ECEES Second European conference on earthquake engineering and seismology
No full textThe research presented in this paper deals with the seismic retrofitting of existing frame structures by
means of passive energy dissipation. An iterative displacement-based procedure, based on capacity
spectrum is described and some applications are discussed. The procedure can be used with any
typology of dissipative device and for different performance targets. In this work the procedure has
been applied to an existing r.c. frame building, which shows both vertical and plan irregularities. In the
application presented the buckling restrained braces have been used in order to prevent damages to
both the structure and non structural elements. The evaluation of commonly Nonlinear Static
Procedures (NSPs) for seismic response of the existing and retrofitted structure is presented to check
the suitability of the use of NSP in the design procedure: the use of conversional NSPs to be not
suitable for the case of irregular building but, once this building is retrofitted, and therefore
regularized, with a bracing system, the use of NSPs for seismic response of the braced structure is
effective
A design procedure of dissipative braces for seismic upgrading structures
No full text"Existing reinforced concrete frame buildings with non-ductile detailing could suffer severe damage and caused loss of life during earthquakes. In recent years many research activities have been paid to develop innovative and more reliable structural control devices and different rehabilitation systems have been studied to upgrade the seismic performance of this kind of structures. The research discussed in this paper deals with the seismic protection of frame structures by means of passive energy dissipation. A displacement-based procedure to design dissipative bracing for the seismic protection of frame structures is proposed and some applications are discussed. The procedure, based on the displacement based design and using the capacity spectrum method, aims to be used as a professional tool as it does not require sophisticated dynamic nonlinear analyses but only common non linear static analyses. Two performance objective have been considered developing the procedure: to protect the structure against structural damage or collapse and avoid non-structural damage, this is done limiting global displacements and interstorey drifts. In the paper the argument is discussed and compared to other different existing approaches. After the presentation the procedure is applied to case studies. The applications are: two 2D r.c. frames, one infilled and one bare, and finally a real application on an existing 3D.
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